Is this wrong?

Not quite sure I know exactly what you are looking for, but sometimes I follow the search word with the letters 'faq'. That is, frequently asked questions. That eliminates many of the advertising sites.

Sometimes.

You'd say "If I'm looking for a specific piece of information" or else, "If I'm looking for specific information" without the "a".



I'd phrase it this way:

"Although they usually have a lot of advertisements if I'm looking for specific information I search through blogs."

We say "information" is a collective noun, like deer or hair or rain, and others. So we don't say "a information" because it is neither singular nor plural. We might combine it with a noun:
* a bit of information
* a word or two of information

"Although" usually introduces a comparison. "Although they have advertisements, I read them anyway."

"If I'm looking for specific information I search through blogs. But they usually have a lot of advertisements.